Liquid mixtures based on ethylene polymers, a process for producing them and a coating or bonding process in which they are used

ABSTRACT

The liquid mixtures according to the invention comprise at least one ethylene polymer (A) and at least one solvent (B), and are characterized in that: 
     (a) the ethylene polymer (A) comprises at least one terpolymer having a fluidity index comprised between 2 and 500 dg/min and comprising: 
     from 83 to 95.7 moles % of units derived from ethylene, 
     from 4 to 15 moles % of units derived from at least one alkyl acrylate or methacrylate, the alkyl group having from 1 to 6 atoms of carbon, and 
     from 0.3 to 2 moles % of units derived from maleic anhydride, 
     (b) the solvent (B) is selected from amongst aliphatic, cycloaliphatic and aromatic hydrocarbons having from 5 to 12 atoms of carbon, dechlorinated solvents and esters. 
     The process comprises in a first step the dissolution of polymer (A), by stirring, in the solvent (B) at a temperature T (expressed in Celcius degrees) such that: 35≦T≦θ, θ being the boiling temperature of the solvent (B). 
     Application to the coating of a support or to the bonding of two substrates by steeping in or spraying of a liquid mixture comprising a solvent and, optionally, evaporation of said solvent.

The document US-A-4,001,159 describes an aqueous dispersion of anolefin-acrylate copolymer comprising from 5 to 60 mol% of an olefincontaining from 3 to 20 carbon atoms, from 40 to 95 mol% of acrylate andfrom 0 to 30 mol% of a compound chosen from acryloyl halides and maleicanhydride, the said copolymer being present in a proportion of 1 to 300parts by weight per 100 parts by weight of water. Since theolefin-acrylate copolymer is soluble in many solvents such ashydrocarbons, esters, ketones, amides, ethers and halogenatedhydrocarbons, the aqueous dispersion may be produced by first preparinga solution with a viscosity ranging up to 60 poises and then dispersingthe solution in water and, finally, removing the solvent. To produce astable aqueous dispersion, the dispersion must be performed in thepresence of a preferably nonionic or anionic surface-active agent, usedin a proportion of 0.1 to 20% by weight relative to the olefin-acrylatecopolymer.

Document FR-A-2,386,402 describes a process for coating a substrate witha layer of polymer, the said process comprising:

(a) the preparation of a suspension of polymer in an organic liquid,

(b) the coating of the substrate using the said suspension of polymer,

(c) the removal of the organic liquid; the said process beingcharacterized in that the polymer suspension is obtained by quenching asolution of the said polymer. The polymers envisaged include apolyethylene grafted with a small quantity of an unsaturated carboxylicacid such as (meth)acrylic acid. The organic liquid may be a solvent forthe said polymer, such as, in particular, a paraffinic hydrocarbon. Thepolymer concentration in the suspension is preferably below 8% byweight. The quenching operation is preferably performed at a temperaturenot exceeding 50° C.

A first object of the present invention consists of liquid mixturescomprising at least one ethylene polymer (A) and at least one solvent(B), which are characterized in that:

(a) the ethylene polymer (A) comprises at least one terpolymer having aflow index of between 2 and 500 dg/min and comprising:

some 83 to 95.7 mol% of units derived from ethylene, from 4 to 15 mol%of units derived from at least one alkyl acrylate or methacrylate, thealkyl group containing from 1 to 6 carbon atoms, and from 0.3 to 2 mol%of units derived from maleic anhydride,

(b) the solvent (B) is chosen from aliphatic, alicyclic and aromatichydrocarbons containing from 5 to 12 carbon atoms, esters andchlorinated solvents.

According to a preferred embodiment of the present invention, theterpolymer has a number average molecular mass Mn which is greater thanor equal to 5,000 and/or a polydispersity index (defined as the ratio ofthe weight average molecular mass Mw to Mn and calculated from thedistribution curve of molecular masses, which is obtained by gelpermeation chromatography) greater than 5. As possible examples ofsolvents (B) there may be mentioned, in particular: n-pentane, n-hexane,methylcyclohexane, n-heptane, xylene, styrene, white spirit, ahydrocarbon cut containing from 9 to 12 carbon atoms such as thatmarketed under the trademark Isopar, phthalate esters such as butylphthalate, and chlorinated solvents such as trichloroethylene andperchloroethylene.

The liquid mixtures according to the invention may be divided up intotwo categories:

on the one hand, the homogeneous solutions of at least one ethylenepolymer (A) in at least one solvent (B), and

on the other hand, the aqueous emulsions produced from theabovementioned homogeneous solutions.

In order to retain the ease of use of the homogeneous solutions, it isdesirable that their viscosity should not exceed a certain limit, as isknown to the specialist. For this reason, the concentration of theterpolymer in the solvent (B) is preferably lower than or equal to 40%by weight, this limit being the lower the lower the flow index of theterpolymer and the lower the temperature; for example, the concentrationof a terpolymer with a flow index equal to 7 dg/min should not exceedapproximately 15% by weight at 30° C. However, by starting with thepolymer (A) as defined above, it is possible to obtain more concentratedsolutions (for example 50% by weight) which are particularly suitablefor being converted into emulsions.

The liquid mixtures according to the invention may furthermore compriseat least one (colouring pigment) (such as a phthalocyanine) in aproportion which is lower than or equal to 2% by weight based on thepolymer (A) and/or at least one (agent for modifying or crosslinking)the polymer (A) (such as a heavy alcohol, a mono-, di- ortrialkanolamine, or alternatively a polyfunctional alcohol) in aproportion which is lower than or equal to 2 mol% based on the polymer(A).

The aqueous emulsions according to the invention comprise from 50 to 200parts by weight of water containing at least one (surface-active agent,)per 100 parts by weight of the mixture of polymer (A) and solvent (B).The surface-active agents which may be used for the emulsions accordingto the invention are preferably nonionic agents such as polyetheroxides; they are generally present in a proportion of 0.5 to 10% byweight based on the polymer (A). The emulsions according to theinvention may additionally comprise, on the one hand, at least one(antifoaming agent) such as methanol in a proportion of at most 5% byweight based on the water and, on the other hand, at least one (agentfor chemically modifying) the terpolymer, such as aqueous ammonia, in aproportion of at most 2 mol% based on the terpolymer. The emulsionsaccording to the invention additionally preferably comprise at least one(water-soluble polymeric stabilizer) such as a polyacrylamide, partiallyionized or otherwise, a polyvinyl alcohol or a cellulose ether, in aproportion of 0.01 to 0.2% by weight based on water.

A second subject of the present invention is a process for producing theliquid mixtures described earlier, characterized in that, in a firststage, it comprises dissolving the polymer (A), by stirring, in thesolvent (B) at a temperature T (expressed in degrees centigrade) suchthat:

    35≦T≦θ,

θ being the boiling temperature of the solvent (B). The solutionsproduced using this process are completely homogeneous and may be cooleddown to ambient temperature without losing their homogeneity.

To produce aqueous emulsions, the process according to the invention ischaracterized in that it comprises, in a second stage, the gradualaddition, with intense stirring, at a temperature of between 35 and 100°C., of a mixture of water, surface-active agent and, if appropriate, anantifoaming agent and/or a chemical modifier. The water-solublepolymeric stabilizer may be added either during or after this secondstage.

According to a preferred alternative form, the aqueous emulsions areobtained by introducing the solution of polymer (A) and of solvent (B)into the aqueous phase.

A third subject of the present invention consists of a process forcoating a substrate by dipping into or by spraying a liquid mixturecomprising at least one ethylene polymer (A) in at least one solvent(B), characterized in that the said liquid mixture is a mixture such asdescribed earlier. When the liquid mixture employed is a solution in asolvent with a low boiling point, the coating is ultimately obtainedafter evaporation of the said solvent. It is also possible to obtain acoating without evaporation of the solvent if the latter is a solventwhich has a high boiling point and if the concentration of polymer (A)is high (for example at least equal to 30% by weight). Examples of suchsolvents are: a saturated C₁₀ -C₁₂ hydrocarbon cut, flux oils, and butylphthalate. When the liquid mixture employed is an aqueous emulsion, thecoating process according to the invention comprises the evaporation ofthe water and, where appropriate, that of the solvent if a solventhaving a low boiling point is involved.

The substrates to which the coating process according to the inventionis applicable may be of various natures: metals, synthetic resins,glass, and the like.

The coating process according to the invention may, in particular, beadvantageously used to protect (against glass splinters) receptaclessuch as, in particular, test tubes, user-openable pharmaceuticalampoules, for the adhesive-coating of wires or fibres or metalcomponents used in the manufacture of rubber or elastomeric articlessuch as, in particular, tire reinforcements, and for sizing glass fibresused, for example, as a reinforcing agent for thermoplastic materials.

The coating process may result either in protection due to an adhesivecoating or protection of the substrate due to a nonadhesive coating.This second variation is of particular interest for the protection ofmetal surfaces against impacts and scratches. After the equipmentcomprising these protected metal surfaces has been installed, theprotective coating may be readily removed simply by being peeled off. Toproduce this result, the solutions according to the invention contain asmall quantity of a release agent; silicone oil may be used, for examplein concentrations of the order of 0.5% based on the solution.

Another subject of the invention consists of a process for bonding twosubstrates by means of an adhesive, characterized in that the adhesiveconsists of a solution or of an emulsion such as have been describedabove or of the product obtained after evaporation of the solvent and,where applicable, of the water.

Thus, a substrate may receive an adhesive coating and the latter may beused to receive a second substrate, being thus responsible for thebonding between the two substrates. In an application of this type, asecond substrate which can be mentioned may be:

an ink (the coating according to the invention is then used as a primercoating on, for example, a nonprintable polymer such aspolyethyleneterephthalate), or a textile (the coating according to theinvention may thus be used for fusible printing for interlining.

The following examples are given by way of illustration and withoutlimiting the present invention. The parts are parts by weight, unlessstated otherwise.

EXAMPLE 1

1 part of a terpolymer with a flow index of 4 dg/min and comprising 89mol% of ethylene, 10 mol% of ethyl acrylate and 1 mol% of maleicanhydride, is dissolved at 40° C. in 10 parts of xylene, with stirring.The terpolymer used has a molecular mass Mn of 18,000. The solutionobtained retains its homogeneity after cooling to ambient temperature.

EXAMPLE 2

The polymer solution prepared in accordance with Example 1 is used tocoat a steel plate with adhesive by dipping followed by drying undervacuum. This plate is then bonded, using heat-bonding at 120° C. at 10bars and for 5 minutes, to a 1.6 mm thick sheet of anethylene/propylene/diene rubber with a flow index of 0.2 dg/min,marketed under the trademark Dutral 054.

The peel strength of the rubber, measured in accordance with the ASTMstandard D 903-49, is 2.5 kg/cm.

EXAMPLE 3 (COMPARATIVE)

The experiment in Example 2 is repeated without applying the adhesivecoating to the steel plate. The peel strength of the rubber, measuredaccording to ASTM standard D 903-49, is 0.05 kg/cm.

EXAMPLE 4

The experiment in Example 2 is repeated, with the following exceptions:

the rubber is formulated, in a manner known per se, with the use ofsulphur and of carbon black with a view to subsequent vulcanization, thethickness of the rubber sheet is 3 mm, and the heat-bonding is performedat 180° C. at the same time as the vulcanization.

The peel strength of the vulcanized rubber, measured according to ASTMstandard D 903-49, is 3.5 kg/cm.

EXAMPLE 5 (COMPARATIVE)

The experiment of Example 4 is repeated without applying an adhesivecoating to the steel plate. The peel strength of the vulcanized rubber,measured according to ASTM standard D 903-49, is 0.05 kg/cm.

EXAMPLE 6

A solution containing 40 parts of a terpolymer with a flow index of 70dg/min and containing 94.3 mol% of ethylene, 4.7 mol% of butyl acrylateand 1 mol% of maleic anhydride and 60 parts of butyl phthalate isproduced by mixing the constituents with stirring at 60° C.

A steel component is dipped in the solution which is heated to 100° C.On cooling, the solution gradually solidifies to form a waxy solidhaving good adhesion to the steel, without removal of the solvent.

EXAMPLE 7

0.5 parts of silicone oil are added to 100 parts of the solutionobtained in Example 6. After application under the same conditionsfollowed by cooling, a readily peelable protective film is obtained; thesurface of the steel component is unchanged.

EXAMPLE 8

A solution is produced, containing 50 parts of a terpolymer with a flowindex of 150 dg/min and comprising 92.3 mol% of ethylene, 6.7 mol% ofethyl acrylate and 1 mol% of maleic anhydride, and 50 parts of xylene.

48 parts of this solution are poured into an aqueous phase containing 48parts of water, 0.24 part of NH₄ OH, 1.9 parts of methanol, 1.2 parts ofa propylene oxide/ethylene oxide emulsifier and 0.09 part of acopolyacrylamide stabilizer, 40% of which is in ionized form.

The emulsion is applied as a dot pattern onto a cloth through a grid andis then dried very rapidly. The coated cloth obtained is then passedover a calender roll heated to 180° C. at the same time as anothercloth, to which the coated cloth adheres firmly.

The same emulsion is applied in the same manner after diethanolamine hasbeen added to it in a quantity corresponding to double thestoichiometric quantity based on the anhydride groups.

A lamination which is particularly resistant to cleaning solvents isobtained in this manner.

What is claimed is:
 1. A process for bonding two substrates by means ofan adhesive, characterized in that the adhesive is a liquid mixtureconsisting essentially of at least one ethylene polymer (A) and at leastone solvent (B), wherein:(a) the ethylene polymer (A) comprises at leastone terpolymer with a flow index of between 2 and 500 dg/min, theterpolymer consisting essentially of:from 83-95.7 mol% of units derivedfrom ethylene, from 4-15 mol% of units derived from at least onealkylacrylate or alkyl methyacrylate, the alkyl group containing 1 to 6carbon atoms, and from 0.3 to 2 mol% of units derived from maleicanhydride, (b) the solvent (B) is chosen from aliphatic, alicyclic andaromatic hydrocarbons containing from 5 to 12 carbon atoms, esters andchlorinated solvents.
 2. A liquid mixture comprising:(a) at least oneethylene polymer (A) comprising at least one terpolymer with a flowindex of between 2 and 500 dg/min, the terpolymer comprising:(i) from 83to 95.7 mol% of units derived from ethylene; (ii) from 4 to 15 mol% ofunits derived from at least one alkyl acrylate or alkyl methacrylate,the alkyl group containing from 1 to 6 carbon atoms; and (iii) from 0.3to 2 mol% of units derived from maleic anydride; (b) at least onesolvent (B) chosen from aliphatic, alicyclic and aromatic hydrocarbonscontaining from 5 to 12 carbon atoms, esters and chlorinated solvents;and (c) a release agent.
 3. The liquid mixture according to claim 2,wherein the release agent is silicone oil.
 4. A liquid mixturecomprising:(a) at least one ethylene polymer (A) comprising at least oneterpolymer with a flow index of between 2 and 500 dg/min, the terpolymercomprising:(i) from 83 to 95.7 mol% of units derived from ethylene; (ii)from 4 to 15 mol% of units derived from at least one alkyl acrylate oralkyl methacrylate, the alkyl group containing from 1 to 6 carbon atoms;and (iii) from 0.3 to 2 mol% of units derived from maleic anhydride; (b)at least one solvent (B) chosen from aliphatic, alicyclic and aromatichydrocarbons containing from 5 to 12 carbon atoms, esters andchlorinated solvents; and (c) from 50 to 200 parts by weight of watercontaining at least one surface-active agent per 100 parts by weight ofthe mixture of the polymer (A) and the solvent (B).
 5. The liquidmixture according to claim 4, characterized in that the surface-activeagent is a nonionic agent which is present in a proportion of 0.5 to 10%by weight based on the polymer (A).
 6. The liquid mixture according toclaim 4, characterized in that the liquid mixture further comprises atleast one antifoaming agent in a proportion of at most 5% by weightbased on the water.
 7. The liquid mixture according to claim 4,characterized in that the liquid mixture further comprises at least oneagent for modifying the terpolymer chemically in a proportion of at most2 mol% based on the terpolymer.
 8. The liquid mixture according to claim4, characterized in that the liquid mixture further comprises at leastone water-soluble polymeric stabilizer in a proportion of 0.01 to 0.2%by weight based on the water.
 9. A process for bonding two substratescomprising the steps of applying an adhesive to at least one of saidsubstrates, wherein the adhesive is a liquid emulsion of claim 4 or isthe product obtained after evaporation of the solvent and evaporation ofthe water in the liquid emulsion of claim 4, and bringing said twosubstrates together to be bonded by said adhesive.
 10. A process forproducing aqueous emulsions according to claim 4, comprising the stepsof in a first stage, dissolving the polymer (A), by stirring, in thesolvent (B) at a temperature expressed in degrees centigrade such that35≦T≦θ, θ being the boiling point temperature of the solvent (B), and ina second stage, gradually adding, with intensive stirring at atemperature of between 35° and 100° C., a mixture of water and asurface-active agent.
 11. The process according to claim 10, wherein thewater and the surface active agent are added with at least one additiveselected from an antifoaming agent and a chemical modifier.
 12. Aprocess for producing aqueous emulsions according to claim 4, comprisingthe steps of in a first stage, dissolving the polymer (A), by stirring,in the solvent (B) at a temperature expressed in degrees centigrade suchthat 35≦T≦θ, θ being the boiling point temperature of the solvent (B),and in a second stage, gradually adding with stirring the solutionproduced in the first stage, at a temperature of between 35° and 100°C., into a mixture of water and a surface-active agent.
 13. The processaccording to claim 12, wherein the water surface active agent is addedwith at least one additive selected from an antifoaming agent and achemical modifier.